Trayana Hristova
Author
In a previous article, we briefly touched on the different areas in which neuroengineering can be applied and how this can better and deepen our understanding of the nervous system, as well as the more practical side of the research that is being conducted. The biggest and probably one of the most promising facets of this subject is the prospect of enabling patients with spinal cord injury (SCI for short) to walk again. In order for us to understand how this is possible, we must first take a deeper look into why such an injury can leave a person paralyzed to begin with.
The first thing to look at is the spinal cord itself. This thin tube along our backs contains a total of 31 pairs of nerves and nerve roots, each of which has a specific purpose. They are meant to send electrical signals between our brains and the rest of our body, thus controlling practically every activity in the human body – from being in charge of the sensations of hot and cold to regulating essential body mechanisms such as breathing or bowel movements. The so-called spinal roots are the ones that branch off from the spinal cord, dividing the body into 5 main sections – cervical, thoracic, lumbar, sacral and coccygeal. Fancy names aside, these nerves determine the actions of the muscles in a certain area. An injury that occurs in the cervical area results in paralysis of the entire body, also known as quadriplegia, where all four limbs, as well as the trunk, are all affected. The same is true for the thoracic area, whereas injuries in the lumbar and sacral result in paraplegia (in which the trunk and the legs are affected). After injuries like these the messages from the brain don’t reach the nerves at all making treatments for these conditions extremely challenging.
It wasn’t until last year that a team of Swiss researchers, led by Grégoire Courtine and Jocelyne Bloch of the Swiss Federal Institute of Technology in Lausanne (EPFL) managed to program a specific device capable of sending electrical signals to a specific target in the injured region and reactivate it, helping patients to move again. This implant in question is a nerve-stimulating device that is controlled by software.
As stated earlier, after a spinal cord injury, the messages from the brain have trouble propagating to a muscle so that it can contract. However, all of those messages are nothing more than electrical impulses generated over a very short period of time. That’s why researchers had already been trying to stimulate the nerves through the back of the spine by using broad electrical fields emitted by devices originally designed to control chronic pain (a practice called spinal cord stimulation (SCS)).
The Swiss-based team of researchers redesigned the devices in such a way that the electrical impulses were targeted at the dorsal part of the spine (i.e. the back of the spine), allowing for a much more specific targeting of the relevant area and thus, activation of the spinal cord. The implant is connected to a computer where the stimulation algorithms would be able to instruct the device on what signal to emit in order to stimulate the nerve. This technique is known as EES (epidural electrical stimulation) where an electrical pulse is used to artificially stimulate the nerve on the surface of the dura mater, a layer of tissue which surrounds the spinal cord.
The advancements in the field are coming at a spectacular rate. With the emergence of companies such as Onward Medical (co-founded by Prof. Courtine and his team) these systems are in demand more than ever. That’s why more research is needed in the field of non-invasive electroencephalogram (EEG)-based brain-computer interfaces (BCI), and we impatiently await the breakthroughs to come and the improvement they will bring to the lives of SCI patients.